Chiral indole intermediates and their fluorescent cyanine dyes containing functional groups

ABSTRACT

This invention relates to the functionalized cyanine dyes and more particularly, to the synthesis of chiral 3-substituted 2,3′-dymethyl-3H-indole and its derivatives as intermediates for preparation of cyanine dyes, to methods of preparing these dyes and the dyes so prepared.

This application is the U.S. national phase of international applicationPCT/US2003/014632, filed 9 May 2003, which claims benefit of U.S.Provisional Application Ser. No. 60/379,107, filed May 10 2002, theentire contents of each of which are incorporated herein by reference.

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of NIH Grant No.R01-NS-19353 and NSF Grant No. MCB-8920118.

This invention relates to the functionalized cyanine dyes and moreparticularly, to the synthesis of chiral 3-substituted2,3′-dimethyl-3H-indole and its derivatives as intermediates forpreparation of cyanine dyes, to methods of preparing these dyes and thedyes so prepared.

Highly fluorescent carboxyl containing indocyanines are useful aslabeling reagents for biological investigations. Functional groups onthe dyes permit covalent binding to biomaterials and/or othernon-biological materials for purpose of fluorescence detection, whilewater soluble arylsulfonate groups reduce dye-dye aggregation andenhance fluorescence brightness (see US patents by Waggoner et. al U.S.Pat. Nos. 5,268,486; 5,486,616; 5,569,587; 5,852,191; 5,981,747;5,986,093).

The carboxylic and arylsulfonate groups occupy key positions in theheteroaromatic bases such as R₁ and R₂ in (1), and thereby restrict theability for dye modifications.

wherein R₁ is CH₂NH₂, CH₂COOH, SO₃H or H and R₂ is (CH₂)_(m)NH₂,(CH₂)_(m)COOH, (CH₂)_(m)SO₃H or (CH₂)_(m)OH, and m is an integer rangingfrom 1 to 6.

Thus, it is of interest to synthesize compounds with functional groupsat different sites in the indole bases. These new intermediates willenable chemists to synthesize a wide range of cyanines.

Chiral 2,3-dimethyl-3H indoles (2) are expected to possess exceptionaladvantages as a precursor of a family of cyanine dyes for use ascovalently attached fluorescent labels for biological research.Disclosed herein is a convenient synthesis of various 3-substituted2-butanones and their conversion to cyanine dyes (FIG. 1). These dyesare very similar to those described in the U.S. Pat. No. 5,268,486 andother related publications of the inventor, such as, for example, listedherein which disclose luminescent mono- and polymethine-cyanine andrelated dyes such as merocyanine and styryl dyes which contain groupsenabling these dyes to covalently attach to amine, hydroxyl, aldehydeand sulphydryl groups on a target material. The disclosed compoundsfluoresce in the green, orange, red and near infrared regions of thespectrum.

-   -   R₁=—CH₂NH₂, —CH₂COOH, —SO₃H, H, —NO₂ or X (Cl, Br, or I)    -   R₂, R₃=—(CH₂)_(m)NH₂, —(CH₂)_(m)COOH, —(CH₂)_(m)SO₃H,        —(CH₂)_(m)OH, —CH₂X (Cl, Br, I), or H        wherein m is an integer ranging from 1 to 6.

Rosenstock (Research Laboratories, The National Drug Company, NOTES(December 1966 pp. 537-539) has described the synthesis of a plantgrowth hormone by means of Fischer indolization of levulinic acidphenylhydrazone. The indole is used for the development of various plantgrowth hormones.

WO 02/26891 discloses cyanine dyes incorporating similar structures.

A number of papers, such as Eggers et al (Angew. Chem. Int. Ed. Engl.(1997) 36, No. 8, 881-883), Eggers et al (Liebigs Ann. (1996), 979-983),Reichardt et al (Chem. Rev. 123, (1990), 565-581), Reichardt et al(Liebigs Ann. (1995) 329-340), and U.S. Pat. Nos. 6,190,641; 6,183,726;6,180,087; 6,180,086 and 6,180,085 have described the synthesis ofchiral indoles such as (3). Cyanine dyes described in these papers arewater insoluble and have no functional groups that react with biologicalspecimens. The chiral indoles are obtained by direct alkylation of2,3-dimethylindole as shown below. This method has very limitedapplications. Attempts to alkylate 2,3-dimethylindole with variousalkylhalides (such as 6-iodo ethylhexanoate) have been unsuccessful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: A General scheme for the synthesis of 3-substituted-2-butanoneand its cyanine dyes.

FIG. 2: Computer generated energy minimized structure of6-(1,2-dimethyl-7-sulfohydrobenzo[e]indolyl)hexanoic acid. The hexanoicacid chain is almost perpendicular to the benzindole ring. Such aconfiguration of the chain prevents dye-dye aggregation.

FIG. 3: ¹H NMR spectra in CDCl₃ of6-(2,3-dimethyl-3H-indol-3-yl)hexanoic acid and5-(2,3-dimethyl-3H-indol-3-yl)pentan-1-ol show identical aromaticsignals. Some of the methylene protons of the hexanoic acid and pentanolalkyl chains show high field shift, suggesting shielding of thoseprotons due to ring current effect of the indole.

FIG. 4: ¹H NMR spectra of Cy3.18 and NS Cy3 in D₂O. Some of themethylene protons of the hexanoic acid chain in NSCy3 show high fieldshift, suggesting shielding of those protons due to ring current effectof the indole.

FIG. 5: Absorption spectra of non-sulfonated Cy3 isomers and theirantibody conjugates.

FIG. 6: Relative fluorescence intensities of non-sulfonated Cy3 isomersNCy3, Cy3.10 and Cy3.24. The absorbance for all dyes in methanol and PBSsolution at 550 nm is 0.05 and the excitation wavelength is 514 nm

FIG. 7: Absorption spectra of Cy7.18 free acid (dotted line) and its IgGconjugate (solid line) are shown in (A). Absorption spectra of NCy7 freeacid (dotted line) and its IgG conjugates (solid line) are shown in (B).NSCy7 showed less dye-dye aggregation (indicated by low vibronicshoulder).

FIG. 8: Antibody brightness of NCy3. The brightness is a product ofnumber of dyes per protein, extinction coefficient of the dye andquantum yield of the dye/antibody conjugates.

FIG. 9: is a graph showing the emission spectra of Cy3.18.OH and thedisulfonated dye (NSCy3) in methanol and phosphate buffer solution whensolutions of equal concentrations were excited at 514 nm. NSCy3 is20-25% brighter than Cy3.18 in both solutions.

The FIGS. 2-9 emphasize improved properties of the cyanine dyes of thepresent invention due to the modifications at the 3, 3′ positions of theindolenine. Specifically, FIG. 2 shows a computer generated, energyminimized structure of6-(1,2-dimethyl-7-sulfo-3-hydrobenz[e]indolyl)hexanoic acid. Thehexanoic acid chain is perpendicular to the plane of benzindole ring.Some of alkyl protons of the hexanoic acid chain are over the plane ofthe ring. This is also substantiated by the NMR spectrum of5-(2,3-dimethyl-3H-indol-3-yl)pentan-1-ol (Example 9) and6-(2,3-dimethyl-3H-indol-3-yl)hexanoic acid (Example 3) in FIG. 3. Thealkyl chain protons or hexanoic acid and pentanol are shielded due toindole ring and therefore appear at high field (0.5-0.7 ppm). In FIG. 4,the NMR of NSCy3 shows similar up-field protons (shown by arrow). Thehexanoic acid protons for Cy3.18 appear at 1.5-2.0 ppm. Such aconfiguration prevents dye-dye aggregation thereby increasing thefluorescence brightness of the dye in aqueous solutions. This is a majoradvantage of these new intermediates of this invention. FIG. 5 shows theabsorbance spectra of three non-sulfonated Cy3 dyes and their IgGconjugates. Cy3.10-IgG conjugates (FIG. 5C) show considerable deviationfrom the base line suggesting significant dye-dye aggregation. Thespectrum Cy3.24 and its IgG conjugates (FIG. 5B) and NCy3 and its IgGconjugates (FIG. 5A) are almost identical. But NCy3 is 20-25% brighterthan Cy3.24 in aqueous solution. This is shown in FIG. 6. The equalconcentration of the dyes in methanol and PBS solutions were excited at514 nm; fluorescence intensities of the dyes in methanol are almost theequal. Because of high solubility in methanol, no dye-dye aggregation isobserved. However, in a phosphate buffer solution, NSCy3 is 20-25%brighter than Cy3.24. The reduction of dye-dye aggregation in anantibody conjugated dyes is also evident from FIG. 7. The absorptionspectra of commercialized Cy7.18 and new NSCy7 are compared with theirantibody conjugates. Cy7.18 aggregates more on antibody as seen from theincrease in the vibronic shoulder.

The present invention provides molecules, such as compounds of formula(I)

which include a reactive or water solubilizing site at R₃ and/or R₄ instructure (I)

The present invention further provides a method of synthesizing, andsynthesized ketones and indolenines wherein substituent R₃ may be—(CH₂)_(t1) A and substituent R₄ may be —(CH₂)_(t2)B, wherein t₁ and t₂are an integer, preferably from 1-22, and A and B are independentlyselected from —COOH, —NH₂, —SO₃, —OH, H and halogens as shown in (II).

The present invention also provides a method of synthesizing ketones andindolenines wherein R₃ and/or R₄, of formula (I) for example, is—(CH₂)_(t)CH₃, wherein t is an integer in the range of 0-22, preferably16 to 22, to produce long alkyl chain dyes as membrane potential probes.

The present invention further relates to the synthesis of cyanine,merocyanine and styryl dyes that can be modified to create covalentlabeling reagents dyes, such as shown herein, wherein functional orwater solubilizing groups may be included.

The present invention therefore, provides intermediates for, and methodsof synthesizing cyanine, merocyanine and styryl dyes, such as thoseshown below.

More specifically, the intermediates of the present invention providemethods of synthesizing intermediates and synthesed compounds from thesame, such as the following polymethine cyanine type dyes:

In these structures, Y is selected from the group consisting of O, S,—CH═CH—, >C(CH₃)₂,

and >N—(CH₂)₁₋₁₀R₁₄, wherein R₁₄ is selected from —COOH, —NH₂, —SO₃ ⁻,—OH and halogen;

Z is selected from the group consisting of O and S; and n is an integerselected from the group consisting of 1, 2, 3 and 4.

At least one, preferably only one, and possibly two or more of the R₁,R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groups in each molecule is areactive group for attaching the dye to the labeled component. Areactive group of a compound according to formula (XIII) or (XIV) canreact under suitable conditions with a complementary functional group ofa component, such that the component becomes covalently labelled withthe compound. For certain reagents, at least one of the R₁, R₂, R₃, R₄,R₅, R₆, R₇, R₁₁, and R₁₂ groups on each molecule may also be a groupthat increases the solubility of the chromophore, or affects theselectivity of labeling of the labeled component or affects the positionof labeling of the component by the dye.

In the above formulas, at least one of said R₈ (if any), R₉ (if any) andR₁₀ (if any) and R₁₃ (if any) groups comprises at least one sulfonategroup. The term sulfonate is meant to include sulfonic acid because thesulfonate group is merely ionized sulfonic acid.

Reactive groups that may be attached directly or indirectly to thechromophore to form the R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groupsmay include reactive moieties such as groups containing isothiocyanate,isocyanate, monochlorotriazine, dichlorotriazine, mono- or di-halogensubstituted pyridine, mono- or di-halogen substituted diazine,maleimide, aziridine, sulfonyl halide, acid halide, hydroxysuccinimideester, hydroxysulfosuccinimide ester, imido ester, hydrazine,azidonitrophenyl, azide, 3-(2-pyridyl dithio)-proprionamide, glyoxal andaldehyde.

Halogen and halo groups are selected from fluorine, chlorine, bromineand iodine.

Specific examples of the R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groupsthat are especially useful for labeling components with availableamino-, hydroxy-, and sulfhydryl groups include:

where n is 0 or an integer from 1-10, and at least one of Q or W is aleaving group such as I, Br, Cl.

Specific examples of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groupsthat are especially useful for labeling components with availablesulfhydryls which can be used for labeling antibodies in a two-stepprocess:

where Q is a leaving group such as I, Br, Cl.

where n is an integer from 1-10.

Specific examples of R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groupsthat are especially useful for labeling components by light-activatedcross linking include:

For the purpose of increasing water solubility or reducing unwantednonspecific binding of the labeled component to inappropriate componentsin a sample or to reduce the interactions between two or more reactivechromophores on the labeled component which might lead to quenching offluorescence, any of the R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₁₁, and R₁₂ groupscan be selected from the well known polar and electrically chargedchemical groups. Examples are -E-F where F is hydroxy, sulfonate,sulfate, carboxylate, substituted amino or quaternary amino and where Eis a spacer group such as —(CH₂)_(n)— where n is 0, 1, 2, 3 or 4. Usefulexamples include alkyl sulfonate; —(CH₂)₃—SO₃ ⁻; and —(CH₂)₄—SO₃ ⁻.

The polymethine chain of the luminescent dyes of this invention may alsocontain one or more cyclic chemical groups that form bridges between twoor more of the carbon atoms of the polymethine chain. These bridgesmight serve to increase the chemical or photo-stability of the dye andmight be used to alter the absorption and emission wavelength of the dyeor change its extinction coefficient or quantum yield. Improvedsolubility properties may be obtained by this modification.

The present invention provides compounds of the following generalformula (XII):

wherein:

-   R_(a) and R_(b) are independently selected from V or L-V where

L is a C₁₋₂₂, such as a C₁₆₋₂₁, straight or branched alkyl chain,optionally containing 0, 1 or 2 unsaturations or unsaturated pendent orinterchain groups selected from alkenyl, alkynyl and aryl groups; and

V is selected from hydrogen, halogen, —OH, —NH₂, —SH, —CN,trifluoromethyl, —SO₃ ⁻ phosphate, phosphonate, quaternary ammonium,—NO₂, mono- or di-nitro-substituted benzyl, —COOH, and —NHCOR_(g), whereR_(g) is C₁₋₂₀ straight or branched alkyl; a target bonding group,reactive group, reactive moiety, or NHR_(h) where R_(h) is H, C₁₋₂₀straight or branched alkyl or COOH;

-   T is

wherein each L and V are independently as defined above; and p is 0 oran integer from 1-4.

The scope of reactive groups, reactive moieties and target bondinggroups described and used herein will be appreciated from the presentdisclosure as well as, for example, U.S. Pat. No. 6,133,445 and WO02/26891, the entire contents of each of which is incorporated herein byreference.

The present invention provides pH sensitive cyanines of the followingformula (XIII):

wherein R_(a), R_(d), R_(e) and R_(f) are any R_(a) as defined above; Y,T and R_(b) are as defined above;

-   Z_(a) and Z_(b) are independently, fused

and n is an integer from 1-4. Preferably, n is an integer from 1-3.

The present invention further provides compounds of the followingformula (XIV) wherein R_(a), R_(c), R_(d), R_(f), T, Y, Z_(a) and Z_(b)are as defined above.

More than one R_(a) may be contained on the noted ring and each suchsubstituent may be the same or different. In one embodiment, R_(a) is asulfonate group and p is 1, where sulfonate includes sulfonic acid asthe sulfonate group is merely an ionized sulfonic acid. Where Z_(a) andZ_(b) are fused rings, R_(a), R_(c), R_(d) and R_(f) may be substitutedaround either ring and p, u, r and v are each independently an integerfrom 0-4.

In the above formulas, the number of methine groups determines, in partthe excitation color. The cyclic azine structures can also determine inpart the excitation color. Often, higher values of n contribute toincreased luminescence and absorbance. At values of n above 4, thecompound becomes unstable. Thereupon, further luminescence can beimparted by modifications at the ring structures. When n=2, theexcitation wavelength is about 650 nm and the compound is veryfluorescent. Maximum emission wavelengths are generally 15-100 nmgreater than maximum excitation wavelengths.

The present invention relates to the other substituents, such as R₂=H,and n is an integer from 0 to 4, in structure (I), which may be used toproduce pH sensitive cyanine dyes, such as those described in copendingU.S. patent application Ser. No. 09/589,502, filed Jun. 8, 2000, whichis incorporated herein by reference and discloses, for example,compounds similar but distinguishable from the following formula (XV).

Specifically, for example, the corresponding compounds of the relatedapplication define the substituents at positions 1 and 2 of formula (XV)as >C(C₁-C₄alkyl)₂, sulfur or oxygen.

The present invention further provides dyes, such as the following rigidtrimethine cyanine dyes. Similar but distinct compounds are described inthe U.S. Pat. No. 6,133,445. Compounds of the present invention include,for example, compounds of the following formula (XVI), intermediates andmethods for synthesizing the same.

The corresponding, yet distinct, compounds of U.S. Pat. No. 6,133,445define the substituents at positions 1 and 2 of formula (XVI) as thesame or different and selected from bis-C₁-C₄ alkyl and C₄-C₅ Spiroalkyl substituted carbon, oxygen, sulphur, selenium, CH═CH, and N—Wwherein N is nitrogen and W is selected from hydrogen, a group—(CH₂)_(n)R¹² where n is an integer from 1 to 26 and R¹² is selectedfrom hydrogen, amino, aldehyde, acetal, ketal, halo, cyano, aryl,heteroaryl, hydroxyl, sulphonate, sulphate, carboxylate, substitutedamino, quaternary amino, nitro, primary amide, substituted amide, andgroups reactive with amino, hydroxyl, carbonyl, phosphoryl, andsulphydryl groups. Compounds of the present invention are other thanthose disclosed in U.S. Pat. No. 6,133,445.

Exemplary dyes according to the invention are as follows:

-   i)    2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium    (Example 13);-   ii)    3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium    (Example 14);-   iii)    2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium    (Example 15);-   iv)    3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium    (Example 16);-   v)    3-(5-carboxypentyl)-3-methyl-2-{(1E,3E,5E)-5-[3-methyl-5-sulfo-3-(4-sulfobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-sulfo-1-(4-sulfobutyl)-3H-indolium    (Example 17); and-   vi)    6,7,9,10-tetrahydro-2,14-disulphonato-16,16,18-trimethyl-7aH,8aH-bisindolinium[3,2-a,3′2′-a]pyrano[3,2-c;5,6-c′]dipyridin-5-ium-18-hexanoic    acid (Example 19).

The present invention relates to the energy transfer dyes whereincyanine-cyanine dye conjugates are synthesized such as (XVII). Suchcyanine-cyanine dye complexes have been described in the U.S. Pat. Nos.6,008,373 and 6,130,094.

Target bonding groups, reactive groups and reactive moieties include,amine, hydroxy, thiol, N-hydroxy-succinimidyl ester,N-hydroxy-sulfosuccinimidyl ester, isothiocyanate, anhydride,haloacetamide, isocyanate, monochlorotriazine, dichlorotriazine,optionally substituted pyridine, mono- or di-halogen substituteddiazine, maleimide, aziridine, imidoester, alkylimidate, hydrazidecarbodiimide, azidonitrophenyl, azide, 3-(2-pyridyldithioyproprionamide, glyoxal, aldehyde, maleimide, sulphonyl halide,phosphoramidite, acid halide, hydrazine and carbodimide groups, andgroups reactive with amino, hydroxyl, aldehyde, phosphoryl, orsulphydryl groups which are, for example, covalently attached toproteins, nucleic acids, nucleosides, nucleotides, carbohydrates,sugars, cells, and combinations thereof, and other biological andnon-biological materials, to make the same fluorescent and detectable,as described, for example in U.S. Pat. No. 6,048,982.

V may also be a group which increases the solubility of the chromophoneor affects the selectivity of labeling of the ultimately labeledcomponent or affects the position of labeling of the labeled componentby the dye.

The compounds or dyes of the present invention may be used to label, forexample avidin, streptavidin, antibodies, DNA, RNA, nucleosides,nucleotides or lectins to detect, measure and/or quantify, for example,biotinylated materials, antigens, haptens, carbohydrate groups, DNA, RNAand complementary DNA or RNA, such as described therein.

In another embodiment, the present invention provides acomponent-labeled complex wherein the label is a compound of any one offormulas (III)-(XVII) and the component is an antibody, protein,peptide, enzyme substrate, hormone, lymphokine, metabolite, receptor,antigen, hapten, lectin, avidin, streptavidin, toxin, carbohydrate,oligosaccharide, polysaccharide, nucleic acid, derivatized deoxy nucleicacid, DNA fragment, RNA fragment, derivatized DNA fragment, derivatizedRNA fragment, nucleoside, nucleotide, natural drug, synthetic drug,virus particle, bacterial particle, virus component, yeast component,blood cell, blood cell component, plasma component, serum component,biological cell, non-cellular blood component, bacteria, bacterialcomponent, natural or synthetic lipid vesicle, poison, environmentalpollutant, polymer, polymer particle, glass particle, glass surface,plastic particle, plastic surface, polymer membrane, conductor orsemiconductor.

A cyanine dye or its derivative of the present invention preferablyabsorbs v maximally in the range of 400-950 nm, preferably in the rangeof 420-470 nm, 520-580 nm, 640-680 nm, 740-790 nm or 820-850 nm. In yetanother embodiment, the present invention provides a method offluorescent detection wherein the dye or derivative of the presentinvention is detected or when multiple fluorescent dyes are used, a dyeor derivative of the present invention may be used in conjunction withdyes which do not either fluoresce at the same or similar pH conditionsand/or at the wavelengths of the presently provided dyes or derivatives.

In a further embodiment, the compound of formula (XIII) may be used in afluorescence method for the qualitative and/or quantitative detection ofpH. The method comprises contacting or mixing a dye of formula (XIII)with a composition containing cells, tissues or biological fluid, anddetecting the emitted fluorescence. The presence of a fluorescent signalis indicative of an acidic environment. In one embodiment, the methodmay be used for detecting intracellular environments, such as may becontained in subcellular compartments or structures. Compounds offormula (XIII) or their membrane permeant derivatives may be actively orpassively absorbed by cells where they may be detected by fluorescencedetection. One of ordinary skill will appreciate the variability of cellpermeability properties of compounds according to formula (XIII) andwill be able to routinely test for the same.

The methods according to the present invention may employ known devicesfor illumination and detection at separate defined wavelengths. Suchdevices include fluorescence spectrophotometers, fluorescencemicroscopes. Alternatively, changes in fluorescence intensity may bemeasured by means of a charge coupled device (CCD) imager (such as ascanning imager or an area imager) to image all of the wells of amicrotitre plate.

The present invention is further described by the following examples.

EXAMPLES 1. Synthesis of diethyl 2-acetyl-2-methyloctane-1,8-dioate

In a 1 L three necked flask equipped with a mechanical stirrer andreflux condenser was placed dry toluene (300 ml). The system was flushedwith argon and sodium hydride (Aldrich, 60% dispersion in mineral oil)(7.2 g, 0.18 mmol) was added. Ethyl-γ-methylacetoacetate (Aldrich, 21 g,0.15 mole) was added with stirring over a 30 minutes. The resultingsolution was heated under reflux for 2 hrs and cooled slightly. (Note:Reaction mixture becomes a thick paste and mechanical stirrer isessential). Ethyl 6-bromohexanoate (Aldrich, 33.5 g, 0.15 mol) was added(all at once) and the suspension was heated under reflux for 12 hrs,cooled, filtered and the solvent evaporated under pressure. The residuewas distilled under vacuum to yield 20 g (46%) of colorless liquid, b.p.110-115° C. (0.1 mm). IR (neat): νcm⁻¹=1735 (s) and 1713 (s). ¹H NMR inCDCl₃ δ, 4.1-4.2 (m, 4H, (O—CH₂)₂); 2.1 (t, J=8.4 Hz, 2H, CH₂COO—);2.15(s, 3H, CH₃CO); 1.5-2.0 (m, 4H, (CH₂)₂); 1.2-1.4 (m, 13H, 2 CH₂ andthree —CH₃).

2. Synthesis of 7-acetyloctanoic acid (or 7-methyl-8-oxononanoic acid)

A mixture of diester from Example 1 (15 g, 0.052 mol) in dilutehydrochloric acid (40-50%) (100 ml) was heated to reflux for 12 hrs. Thereaction mixture was cooled and extracted with ethyl acetate (3×100 ml).The organic phase was dried over sodium sulfate, filtered, and ethylacetate was removed. The residue was distilled under reduced pressure,to yield 7.7 g (80%), colorless liquid, b.p. 120-125° C., IR (neat):νcm⁻=1736 (s) and 1710 (s). ¹H NMR, CDCl₃, δ, 2.45-2.55 (q, 1H, J=6.6Hz, 7-H); 2.35 (t, J=7.3 Hz, 2H, —CH₂—COOH); 2.125 (s, 3H, COCH₃);1.65-1.1.75 (m, 2H, —CH₂); 1.23-1.4 (m, 6H, (—CH₂)₃); 1.1 (d, J=5.9 Hz,7-CH₃).

3. Synthesis of 6-(2,3-dimethyl-3H-indol-3-yl)hexanoic acid

To a stirred solution of phenylhydrazine hydrochloride (Aldrich, 7.2 g,0.05 mol) in acetic acid (50 ml) was added 7-acetyloctanoic acid (11 g,0.06 mol). The reaction mixture was heated under reflux for 4 hrs. Thesolution was cooled. (No clear precipitate was observed). Acetic acidwas removed under reduced pressure. The resulting yellow liquid waschromatographed on a silica gel column using chloroform/methanol mixtureas solvent. Pure 6-(2,3-dimethyl-3H-indol-3-yl)hexanoic acid (8.0 g,61%) was obtained as pale yellow oil which crystallized on standing,m.p. 115-118° C.; IR νcm⁻¹=2927, 2860, 2526, and 1709. ¹H NMR, CDCl₃, δ,7.6 (d, 1H, J=7 Hz, 4-H); 7.2-7.4 (m, 3H, aromatic protons); 2.25 (s,3H, —CH₃); 2.1-2.2(t, —CH₂COOH); 1.72-1.94 (m 2H, —CH₂); 1.4-1.45 (m,2H, —CH₂); 1.23-1.05 (m, singlet merged in m, 5H, —CH₂, —CH₃); 0.55-0.85(m, 2H, —CH₂). TLC, Rf=0.22 (silica gel, methanol-chloroform, 5:95).

4. Synthesis of3-(5-carboxypentyl)-2-{(1E,3E)-3-[3-(5-carboxypentyl)-1-ethyl-3-methyl-1,3-dihydro-2H-indol-2-ylidene]prop-1-enyl}-1-ethyl-3-methyl-3H-indoliumiodide (NCy3)

4.1 3-(5-Carboxypentyl)-1-ethyl-2,3-dimethyl-3H-indolium iodide

6-(2,3-Dimethyl-3-hydroindole-3-yl)hexanoic acid (518 mg, 2 mmol) wassuspended in acetonitrile (5 ml) and ethyl iodide (1.2 g, 10 mmol) andthe mixture was heated to reflux with stirring for 1 hr. More ethyliodide (2 g) was added and heating continued for an additional 12 hrs.The mixture was then cooled, and acetonitrile and excess ethyl iodidewere removed on a rotary evaporator. The sticky mass was washed severaltimes with ice-cooled diethyl ether and dried to yield pink amorphouspowder (0.45 g, 78%). The product was used for the next reaction withoutfurther purification.

4.2 To a stirred solution of 6-(1ethyl-2,3-dimethyl-3-hydroindol-3-yl)hexanoic acid (288 mg, 0.95 mmol)in pyridine (10 ml) at 120° C. was added dropwise, triethyl orthoformate(100 mg, 67 mmol) over 30 minutes. After 2 hrs the reaction mixture wascooled and triturated with diethyl ether. The product was purified on asilica gel column using chloroform/methanol mixture as solvent. Themajor compound (Rf=0.45, tlc, silica gel, methanol in chloroform 5%) wasobtained as a pink solid (251 mg, 35%); ¹H NMR, CDCl₃, d, 8.2 (t, H,J=7Hz, (β-H); 7.1-7.6 (m, 8H, aromatic); 6.4 (d, 2H, J=7 Hz, α-H, α′-H);4.2 (m, 4H, 2-NCH₂); 2.2-2.3 (m, 4H, 2-CH₂COOH, 2-CH₂); 1.8 (s, 6H,(—CH₃)₂); 1.43 (t, 6H, J=6.5 Hz, 2-CH₃); 1.1-1.2 (m, 4H, 2-CH₂); 0.5-0.7(m, 4H, 2-CH₂); λmax: 550 nm, methanol.

5. Preparation of 6-(2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid

To a stirred solution of 4-hydrazinobenzenesulfonic acid (Aldrich, 11.25g, 0.06 mol) in acetic acid (50 ml) was added 7-acetyloctanoic acid(16.7 g, 0.09 mol). The reaction mixture was heated under reflux for 12hrs. Acetic acid was removed under reduced pressure. The resulting solidwas dissolved in methanol and reprecipitated with a saturated solutionof potassium hydroxide in isopropanol. The solid was filtered, washedwith isopropanol and dried, (8 g, 40%). The analytical sample wasobtained by C18 reversed phase column chromatography usingwater/methanol mixture as solvent., m.p. 250° C. dec; IR νcm⁻¹=2930,2597, and 1719. ¹H NMR, D₂O, δ, 7.8-7.9 (m, 2H, 4-H and 6-H of aromaticprotons); 7.6 (d, J=7 Hz, 1H, 7-H of aromatic); 2.2 (t, J=7 Hz, 2H,—CH₂—COOH); 1.9-2.1 (m, 2H, alkyl); 1.2-1.6 (a singlet merged in amultiplet, 7H, —CH₃ & (—CH₂)₂); 0.6-0.9 (m, 2H, alkyl).

6. Synthesis of3-(5-carboxypentyl)-2-{(1E,3E)-3-[3-(5-carboxypentyl)-1-ethyl-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]prop-1-enyl}-1-ethyl-3-methyl-3H-indolium-5-sulfonate(NSCy3)

3-(5-Carboxypentyl)1-ethyl-2,3-dimethyl-3H-indolium-5-sulfonate wassynthesized following the procedure described in Example 4.1.6-(2,3-Dimethyl-5-sulfo-3-hydroindole-3-yl)hexanoic acid (680 mg, 2mmol) was suspended in acetonitrile (10 ml) and ethyl iodide (1.2 g, 10mmol) and the mixture was heated to reflux with stirring for 1 hr. Moreethyl iodide (2 g) was added and heating continued for additional 12hrs. The mixture was then cooled and solvent removed on a rotaryevaporator. The sticky mass was dissolved in methanol (5 ml). A solutionof potassium acetate in isopropanol was added until the reaction productwas alkaline to pH. The solid obtained was filtered and washed severaltimes with isopropanol to yield a gray amorphous powder (500 mg, 61%).The product was used for the next reaction without further purification.

To a stirred solution of3-(5-carboxypentyl)1-ethyl-2,3-dimethyl-3H-indolium-5-sulfonate(potassium salt) (400 mg, 0.98 mmol) in pyridine (10 ml) at 100° C. wasadded triethyl orthoformate (100 mg, 66 mmol) over 30 minutes. After 2hours the reaction mixture was cooled and diluted with several volumesdiethyl ether. A product separated as red powder from which supernatantfluid was removed by decantation. It was dissolved in methanol andreprecipitated with isopropanol containing potassium acetate. The crudedye was collected on a filter paper and dried (380 mg, 90%). It waspurified by C18, column chromatography using water-methanol mixture forelution. A pure dye was obtained as pink solid (251 mg), λmax 555 nm; ¹HNMR (D₂O) δ, 8.42 (t, 1H, J=13 Hz, β-H of the bridge); 7.6-7.8 (m, 4H,4-H, 4′-H, 6-H, 6′-4); 7.2 (d, 2H, J=7.7 Hz, 7-H, 7′-H); 6.5 (d, 2H,J=13 Hz, α, α′-H); 4.1 (broad signal, 4H, (N—CH₂)₂); 1.8-2.2 (m, 8H,alkyl and CH ₂COOH); 1.2-1.7 (m, 24H, 6-CH₂, 4-CH₃); 0.45-0.8 (m, 4H,alkyl).

7. Synthesis of ethyl 2-acetyl-7-acetyloxy-2-methylheptanoate

In a 1 L three necked flask equipped with a mechanical stirrer andreflux condenser was placed dry toluene (300 ml). The system was flushedwith argon and sodium hydride (Aldrich, 60% dispersion in mineral oil)(7.2 g, 1.2 eq.) was added. Ethyl-α-methylacetoacetate (Aldrich, 21 g,0.15 mole) was added with stirring over a 30 minutes. The resultingsolution was heated under reflux for 2 hours and cooled slightly. (Note:Reaction mixture becomes a thick paste and a mechanical stirrer isessential). 5-Bromopentylacetate (Aldrich, 31.5 g, 15 mol) was added(all at once) and the suspension was heated under reflux for 12 hr,cooled, filtered and the solvent evaporated under reduced pressure. Theresidue was distilled under vacuum to yield 20 g (45%) of colorlessliquid, b.p 90-92 (0.5 mm). ¹H NMR in CDCl3 δ, 4.1-4.2 (m, 2H, O—CH₂CH₃): 3.5 (t, J=7 Hz, 2H, CH₂OCO—); 2.2 (s, 3H, CH₃CO); 2.1 (s, 3H,—COCH₃); 1.5-2.0 (m, 10H, 4-(CH₂)₂, C—CH ₃, OCH₂ CH ₃).

8. Synthesis of 8-hydroxy-3-methyloctan-2-one or 6-acetyl-octanol

A mixture of diester (15 g, 0.06 mol) in a dilute hydrochloric acid(40-50%) (2100 ml) was heated to reflux for 12 hrs. The reaction mixturewas cooled and extracted with ethyl acetate (3×100 ml). The organicphase was dried over sodium sulfate, filtered, and ethylacetate wasremoved. The residue was distilled in vacuum, to yield 7.19 g (80%)colorless liquid, b.p. 90-97° C. at 0.7 mm, IR (neat): νcm⁻¹=1736; ¹HNMR, CDCl₃, δ, 3.55 (t, 2H, J=6.6 Hz, —CH₂OH); 2.45 (m, 1H, 7-H); 2.15(s, 3H, COCH₃); 1.65-1.82 (m, 4H, (—CH₂)₂); 1.2-1.55 (m, 4H, (—CH₂)₂);1.1 (d, J=7.3 Hz, —CH—CH ₃).

9. Synthesis of 5-(2,3-dimethyl-3H-indol-3-yl)pentan-1-ol

To a stirred solution of phenylhydrazine hydrochloride (Aldrich, 7.2 g,0.05 mol) in acetic acid (50 ml) was added 8-hydroxy-3-methyloctan-2-one(12 g, 0.07 mol). The reaction mixture was heated under reflux for 4hrs. The solution was cooled. (No clear precipitate was observed).Acetic acid was removed under reduced pressure. The resulting yellowliquid was chromatographed on a silica gel column usingchloroform:methanol mixture as solvent. Pure6-(2,3-dimethyl-3-hydroindol-3-yl)pentanol (8.0 g, 60%) was obtained aspale yellow oil; ¹H NMR, CDCl₃, δ, 7.8 (d, J =7 Hz, 4-H aromatic);7.2-7.6 (m, 3H, aromatic protons); 3.5 (t, J=6.5 Hz, —CH₂OH; 2.6 (s, 3H,2-CH₃ of indole); 1.8-2.12 (m, 2 h, alkyl), 1.3-1.7 (singlet merged inmultiplets, 7H, 2 alkyl and —CH₃ of indole); 0.6-0.9 (m, 2H, alkyl).

10. Synthesis of6-(1,2-dimethyl-6,8-disulfo-1H-benzo[e]indol-1-yl)hexanoic acid

(5,7-Disulfo-2-naphthyl)hydrazinium chloride (2.0 g),7-methyl-8-oxononanoic acid (1.5 g) and acetic acid (15 ml) were heatedfrom 80-140° C. for a total of 24 hrs. After evaporation of the solventunder vacuum, the residue was triturated with 2-propanol to give a pinksolid. This solid was collected by filtration, washed with 2-propanol,then excess diethyl ether and dried under vacuum over phosphoruspentoxide. Yield of crude product=1.96 g. This was purified as requiredby preparative HPLC (RPC18. Water/MeCN/TFA) to give pure product. ¹H-nmr(D₂O) δ 0.25-0.4 (1H, broad m), 0.5-0.65 (1H, broad m), 1.00 (2H, m),1.25 (2H, m), 1.78 (3H, s), 2.06 (2H, t), 2.35-2.5 (1H, broad m),2.65-2.8 (1H, broad m), 2.90 (3H, s), 8.05 (1H, d), 8.58 (1H, d), 8.70(1H, d) and (8.97 (1H, d). MS (LCMS) MH+470. Acc. Mass: MH+470.0931(−2.6 ppm for C₂₀H₂₄NO₈S₂).

11. Synthesis of 3-(5-carboxypentyl)-2-{(1 E,3E,5E,7E)-7-[3-(5-carboxypentyl)-1-ethyl-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]hepta-1,3,5-trienyl}-1-ethyl-3-methyl-3H-indolium-5-sulfonate(NSCy7)

Glutaconaldehyde dianil hydrochloride (143 mg, 0.5 mmol) was dissolvedin a heated mixture of acetic anhydride (4 ml) and pyridine (1 ml). Theintermediate 6-(1-ethyl-2,3-dimethyl-5-sulfo-3-hydroindol-3-yl)hexanoicacid (368 mg, 1 mmol) was added and mixture was heated to reflux for anadditional 10 min. and then cooled. The dye was precipitated withdiethyl ether. The supernatant liquid was separated. Solid wasredissolved in a minimum volume of methanol and reprecipitated withisopropanol. The purple solid was collected on a filter paper and dried(160 mg, yield 18%). The pyridinium salt was converted into itspotassium salt and purified by C18 column chromatography usingwater-methanol mixture as eluent. λmax=750 nm.

¹H NMR (D₂O) δ, 7.7 (m, 6H, 4-H, 4′-H, 6-H, 6′-H and γγ′ protons of thebridge); 7.4 (t, 1H, J=13 Hz, β-proton of the bridge): 7.2 (d, 2H, J=7.7Hz, 7-H, 7′-H); 6.35 (t. 2H, J=13 Hz, β, and β′ protons of the bridge,6.15 (d, 2H, J=7 Hz, αα′-H); 4.1 (broad signal, 4H, (N—CH₂)₂); 1.8-2.2(m, 8H, alkyl and CH ₂COOH); 1.2-1.7 (m, 24H, 6-CH₂, 4 CH₃); 0.45-0.8(m, 4H, alkyl). Rf=0.26 (RP-C18, water/methanol-7.5:2.5).

12. Succinimidyl Esters of Carboxyalkyl Cyanine Dyes

The following general procedure was used to prepare succinimidyl estersof Cy3.24.OH, Cy3.10.OH, NCy3, NSCy3, Cy7.18.OH, and NSCy7. A procedurefor making succinimidyl active ester using disuccinimidyl carbonate(DSC) has been described by Ogura, H., Kobayashi, T., Keiko, S., Kawabe.K. and Takeda R. (1979) A novel active ester synthesis reagent(N,N′-Disuccinimidyl carbonate). Tetrahedron Lett. 4745-4746.

In a typical experiment carboxyalkyl indocyanine was dissolved inmixture of dry DMF (2 mL/100 mg dye) and dry pyridine (0.1 mL/100 mgdye). Disuccinimidyl carbonate (DSC) (1.5 eq/carboxyl group) was addedand the mixture was stirred at 55-60° C. for 90 min. under nitrogen.After diluting the mixture with dry ethyl ether, the supernatant wasdecanted. The product was either washed repeatedly with solvent ordissolved in DMF and reprecipitated. Nearly quantitative yields ofcyanine active esters were obtained. The formation of the activesuccinimidyl ester was confirmed by its reaction with benzylamine in DMFor its reaction with taurine in a pH 9.4 bicarbonate buffer. Reversedphase C18 TLC spotted with the conjugate, the succinimidyl ester andhydrolyzed carboxylate product for comparison and developed withwater-methanol mixture. Since activation was sometimes incomplete,reverse-phase HPLC was also used to determine the percentage offluorochrome in the active ester form. The sample was eluted through anAlltech Econosphere 250 mm×4.6 mm C18 RP column using a mixture of 25%acetonitrile and 75% water containing 0.1% trifluoroacetic acid. Thepercentages of activated and unactivated cyanine fluorohore weredetermined by integration of the absorbance signals from a Varian UV/VISdetector.

Alternative procedures for preparing N-hydroxysuccinimidyl esters ofcarboxyalkyl cyanine dyes are described hereinafter, for example, seeExamples 13-16.

13. Synthesis and activation of2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

13.1 6-(2,3-Dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid

4-Hydrazinobenzenesulfonic acid (1.88 g, 10 mmol),7-methyl-8-oxononanoic acid (2.8 g, 15 mmol) and glacial acetic acid (10ml) were mixed and heated under reflux for 6 hrs. The solvent was thenevaporated under vacuum and the residue triturated with diethyl etheruntil a solid was obtained. This was dried under vacuum to give crudeproduct, 3.4 g (100%). This was purified by preparative HPLC as required(RPC18. Water+0.1% TFA→MeCN+0.1% TFA gradient). UV/Vis (Water+0.1% TFA):274, 229, 204 nm. ¹H-nmr (D₂O) δ 0.6-0.9 (2H, broad m), 1.10-1.25 (2H,broad m), 1.35-1.50 (2H, m), 1.60 (3H, s), 2.10-2.40 (2H, broad m+2H,t), 7.77 (1H, d), 7.97 (1H, dd) and 8.06 (1H, d) MS (MALDI-TOF) MH+340.

13.2 4-(2,3,3-Trimethyl-5-sulfo-3H-indolium-1-yl)butane-1-sulfonate

A mixture of potassium 2,3,3-trimethyl-3H-indole-5-sulfonate (5.50 g, 20mmol), 1,4-butanesultone (4.0 ml, 40 mmol) and 1,2-dichlorobenzene (100ml) was mixed and heated at 140° C. for 24 hrs and then 175° C. for 6hrs. After cooling, the magenta solid was collected by filtration,washed with ethyl acetate and dried under vacuum to give 7.97 g (97%) ofproduct. Used without further purification. ¹H-nmr (D₂O) δ 1.62 (6H, s),1.9-2.0 (2H, m), 2.1-2.2 (2H, m), 2.89 (2H, t), 4.55 (2H, t), 7.98 (1H,d), 8.08 (1H, d) and 8.12 (1H, d).

13.34-{2-[(1E,3E)-4-Anilinobuta-1,3-dienyl]-3,3-dimethyl-5-sulfo-3H-indolium-1-yl}butane-1-sulfonate

A mixture of4-(2,3,3-trimethyl-5-sulfo-3H-indolium-1-yl)butane-1-sulfonate (6.20 g),malonaldehyde bis(phenylimine) monohydrochloride (7.8 g), triethylamine(5 ml) and acetic acid (50 ml) was heated at 120° C. for 18 hrs to givea dark brown-red solution. The solvent was evaporated under vacuum andthe residue semi-purified by flash chromatography (silica. Aceticacid/ethanol/water mixtures). Final purification was by HPLC (RPC18.Water+0.1% TFA→MeCN+0.1% TFA gradient). UV/Vis (Water, 50: MeCN, 50:TFA, 0.1) 521 nm. ¹H-nmr (DMSO) δ 1.68 (6H, s), 1.7-1.9 (4H, broad m),2.60 (2H, t), 4.14 (2H, t), 6.36 (1H, t), 6.56 (1H, d), 7.21 (1H, m),7.3-7.5 (5H, m), 7.65 (1H, m), 7.83 (1H, s), 8.39 (1H, t), 8.83 (1H, t)and 11.7 (1H, d). MS (MALDI-TOF) M+504.

13.42-{(1E,3E,5E)-5-[3-(5-Carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

4-{2-[(1E,3E)-4-anilinobuta-1,3-dienyl]-3,3-dimethyl-5-sulfo-3H-indolium-1-yl}butane-1-sulfonate(250 mg) and 6-(2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid (312mg) were mixed in pyridine (9 ml): acetic acid (9 ml): acetic anhydride(2 ml) and stirred at ambient temperature overnight. After evaporationof solvent under vacuum, the residue was then purified twice bypreparative HPLC (RPC18. Water+0.1% TFA→MeCN+0.1% TFA gradient). Theappropriate fractions were pooled and evaporated under vacuum. Theresidue was redissolved in water and freeze-dried to give the purifieddye (135 mg). Observed pKa in aqueous phosphate buffers (viafluorescence): 7.0. UV/Vis (Water+0.1% TFA): 645 nm (ε=2.0×10⁵ l mol ⁻¹cm⁻¹). MS (MALDI-TOF) MH+751. ¹H-nmr (D₂O) δ 0.5-0.65 (1H, broad),0.75-0.9 (1H, broad), 1.1 92H, m), 1.35 (2H, m), 1.5 (3H, s), 1.65 (6H,2×s), 1.75-2.05 (6H, m), 2.1 (2H, t), 2.95 (2H, t), 4.05 (2H, broad t),6.0 (1H, d), 6.2 (1H, d), 6.5 (1H, t), 7.2 (1H, d), 7.3 (1H, d) and7.1-8.1 (6H, m).

13.52-{(1E,3E,5E)-5-[3-(5-Carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium,N-hydroxysuccinimidyl ester

Carboxy dye (30 mg) was dissolved in anhydrous DMF (300 μl); to thiswere added O-(N-succinimidyl)-N,N,N′,N′-tetramethyleneuroniumhexafluorophosphate (HSPyU, 60 mg) and duisopropylethylamine (42 μl).The resulting solution was mixed for 2 hrs, whereupon TLC (RPC18.Water/MeCN/AcOH) revealed complete reaction. The reaction mix wasevaporated under vacuum and the residue was purified by preparative HPLC(Water+0.1% AcOH→MeCN+0.1% AcOH gradient). Fractions containing theprincipal dye peak were pooled and evaporated under vacuum; the residuewas redissolved in water and freeze-dried. UV/Vis (Water, 50: MeCN, 50:TFA, 0.1) 646 nm. MS (MALDI-TOF) MH+˜850.

14. Synthesis and activation of3-(5-carboxypentyl)-2-[(1E,3E,5E5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

14.14-[3-(5-Carboxypentyl)-2,3-dimethyl-5-sulfo-3H-indolium-1-yl]butane-1-sulfonate

6-(2,3-Dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid (340 mg) and sodiumacetate (100 mg) were dissolved in methanol (5 ml), then the solvent wasevaporated under vacuum. The residue was treated with 1,4-butanesultone(680 mg) and 1,2-dichlorobenzene (5 ml); this mixture was heated at 150°C. for 18 hrs under nitrogen. A further aliquot of 1,4-butanesultone(500 mg) was added and heating continued for 4 hrs. After cooling, thesolid product was collected by vacuum filtration, washed withdichlorobenzene and diethyl ether and dried. Crude yield 557 mg. Afterpurification by preparative HPLC (RPC18. Water+0.1% TFA→MeCN+0.1% TFAgradient), the desired product was isolated. ¹H-nmr (DMSO) δ 0.6-0.8(2H, m), 1.05-1.12 (2H, m), 1.43 (2H, app. quin), 1.64 (3H, s), 1.95(2H, aqq. quin), 2.05-2.42 (4H, m+2H, t), 3.01 (2H, t), 4.60 (2H, t),7.97 (1H, d), 8.09 (1H, dd) and 8.13 (1H, d). LCMS: MH+476.

14.24-{2-[(1E,3E)-4-Anilinobuta-1,3-dienyl]-3-(5-carboxypentyl)-3-methyl-5-sulfo-3H-indolium-1-yl}butane-1-sulfonate

4-[3-(5-Carboxypentyl)-2,3-dimethyl-5-sulfo-3H-indolium-1-yl]butane-1-sulfonate(410 mg), malonaldehyde bis(phenylimine) monohydrochloride (500 mg),triethylamine (0.3 ml) and acetic acid (3 ml) were heated at 120° C. for18 hrs to give a dark brown-red solution. The solvent was evaporatedunder vacuum and the residue semi-purified by HPLC (RPC18. Water+0.1%TFA→MeCN+0.1% TFA gradient). The product was then used directly. UV/Vis(Water, 50: MeCN, 50: TFA, 0.1) 523 nm. MS (MALDI-TOF) MH+605.

14.3 5,7-Dichloro-2,3,3-trimethyl-3H-indole

2,4-Dichlorophenylhydrazine.HCl (3.0 g), 3-methyl-2-butanone (3.0 ml)and acetic acid (25 ml) were mixed and heated at 120° C. for 3 hrs. Adark orange solution resulted. The solvent was evaporated under vacuum;the residue was partitioned between ethyl acetate and aqueous sodiumhydrogen carbonate solution. The organic phase was collected, dried(MgSO₄), filtered and the solvent evaporated to give a dark oil.Purification by flash chromatography (silica: ethyl acetate/hexane) gavethe product as a light orange oil, which solidified on standing. ¹H-nmr(CDCl₃) δ 1.31 (6H, s), 2.32 (3H, s), 7.15 (1H, d), 7.26 (1H, s) and7.32 (1H, d).

14.43-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

4-{2-[(1E,3E)₄-Anilinobuta-1,3-dienyl]-3-(5-carboxypentyl)-3-methyl-5-sulfo-3H-indolium-1-yl}butane-1-sulfonate(250 mg) and 5,7-dichloro-2,3,3-trimethyl-3H-indole (230 mg) were mixedwith acetic anhydride (1.0 ml) and DMF (10.0 ml). The mixture wasstirred under nitrogen for 18 hrs, then at 50° C. for 24 hrs. Thesolvent was then evaporated under vacuum; the residue triturated withether, dried and purified by preparative HPLC (RPC18. Water+0.1%TFA→MeCN+0.1% TFA gradient). The appropriate fractions were pooled andevaporated under vacuum to give the product dye, 84 mg. Observed pKa inaqueous phosphate buffers (via fluorescence): 6.05 UV/Vis (Water, 50:MeCN, 50: TFA, 0.1) 646 nm. MS (MALDI-TOF) MH+740.

14.53-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium,N-hydroxysuccinimidyl ester

Carboxy dye (24 mg) was dissolved in anhydrous DMF (2 ml) and evaporatedunder vacuum to ensure dryness.O-(N-Succinimidyl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TSTU,30 mg) was added, along with diisopropylethylamine (25 μl) and DMF (2ml). The red solution was allowed to stand for 1 hr, whereupon TLC(RPC18. Water/MeCN/AcOH) revealed complete reaction. The reaction wasquenched by addition of acetic acid (50 μl) and the solvent evaporatedunder vacuum. The residue was purified by preparative HPLC (Water+0.1%AcOH→MeCN+0.1% AcOH gradient). Fractions containing the principal dyepeak were pooled and evaporated under vacuum; the residue wasredissolved in water and freeze-dried. UV/Vis (Water, 50: MeCN, 50: TFA,0.1) 646 nm. MS (MALDI-TOF) MH+837.

15. Synthesis and activation of2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium

15.1 5-Chloro-2,3,3-trimethyl-3H-indole

4-Chlorophenylhydrazine.HCl (5.4 g), 3-methyl-2-butanone (6.4 ml) andacetic acid (70 ml) were mixed and heated to 80° C. initially, to give asolution. The temperature was then raised to 120° C. over 2 hrs, duringwhich time a solid separated. TLC analysis (RPC18. Water/MeCN/TFA)indicated consumption of the hydrazine starting material and generationof a single main product. After evaporation of the solvent under vacuum,the residue was partitioned between ethyl acetate and aqueous sodiumhydrogen carbonate solution. The organic phase was collected, dried(MgSO₄), filtered and the solvent evaporated to give the crudeindolenine. Purification by flash chromatography (silica. Ethylacetate/hexane) gave 4.66 g (80%) of pure product. MS (MALDI-TOF)M+193,195. ¹H-nmr (CDCl₃) δ 1.30 (6H, s), 2.27 (3H, s), 7.23-7.29 (2H,m) and 7.44 (1H, d).

15.24-(5-Chloro-2,3,3-trimethyl-5-sulfo-3H-indolium-1-yl)butane-1-sulfonate

5-Chloro-2,3,3-trimethyl-3H-indole (1.94 g) and 1,4-butanesultone (5.0g) were mixed in 1,2-dichlorobenzene (15 ml). The resulting solution washeated under nitrogen to 140° C. for 18 hrs, during which time a solidseparated. After cooling to ambient temperature, this solid wascollected by filtration, washed with dichlorobenzene followed by excessdiethyl ether and then dried under vacuum to give the desired product.Yield 2.85 g (86%). MS (MALDI-TOF) MH+330, 332.

¹H-nmr (CD₃OD) δ 1.61 (6H, s), 1.95-1.98 (2H, m), 2.08-2.18 (2H, m),2.88 (2H, t), 4.53 (2H, t), 7.65 (1H, dd), 7.86 (1H, d) and 7.93 (1H, d)

15.34-{2-[(1E,3E)-4-Anilinobuta-1,3-dienyl]-5-chloro-3,3-methyl-3H-indolium-1-yl}butane-1-sulfonate

4-(5-Chloro-2,3,3-trimethyl-5-sulfo-3H-indolium-1-yl)butane-1-sulfonate(0.99 g), malonaldehyde bis(phenylimine).HCl (1.55 g), triethylamine(1.0 ml) and acetic acid (10.0 ml) were mixed and heated at 120° C. for18 hrs to give a dark purple solution. After evaporation of solvent, thecrude reaction product was purified by flash chromatography (silica:MeOH/DCM) to give 1.12 g of pure product. UV/Vis (EtOH): 525 nm. MS(MALDI-TOF) M+458, 460.

15.42-{(1E,3E,5E-5-[3-(5-Carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium

4-{2-[(1E,3E)-4-Anilinobuta-1,3-dienyl]-5-chloro-3,3-dimethyl-3H-indolium-1-yl}butane-1-sulfonate(50 mg), 6-(2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid (50 mg),pyridine (2.25 ml), acetic acid (2.25 ml) and acetic anhydride (0.50 ml)were mixed and incubated at 90° C. for 1 hr, giving a deep bluesolution. The solvent was then evaporated under vacuum and the residuetriturated with diethyl ether. Purification by preparative HPLC (RPC18.Water/MeCN/TFA) yielded two blue components, the first-eluting componenthaving the desired molecular mass and pH-sensitivity. Fractionscontaining this component were pooled and evaporated under vacuum togive the product dye, 16 mg. Observed pKa in aqueous phosphate buffers(via fluorescence): 7.44. UV/Vis (Water, 50: MeCN, 50: TFA, 0.1) 645 nm.MS (MALDI-TOF) M+704, 706.

15.52-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium,N-hydroxysuccinimidyl ester

The carboxy dye (13.5 mg) was dissolved in anhydrous DMF (2 ml) andevaporated under vacuum to ensure dryness.O-(N-Succinimidyl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TSTU,30 mg) was added, together with diisopropylethylamine (25 μl) and DMF (2ml). The orange solution was allowed to stand for 1 hr, whereupon TLC(RPC18. Water/MeCN/AcOH) revealed complete reaction. The reaction wasquenched by addition of acetic acid (50 μl) and the solvent evaporatedunder vacuum. The residue was purified by preparative HPLC (Water+0.1%AcOH→MeCN+0.1% AcOH gradient). Fractions containing the principal dyepeak were pooled and evaporated under vacuum; the residue wasredissolved in water and freeze-dried. UV/Vis (Water, 50: MeCN, 50: TFA,0.1) 645 nm. MS (MALDI-TOF) M+801, 803.

16. Synthesis and activation of3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

16.1 7-Chloro-2,3,3-trimethyl-3H-indole-5-sulfonic acid

2-Chloroaniline-4-sulfonic acid (2.5 g, 9.2 mmol) was dissolved in HCl(conc.; 40 ml) and cooled to 0° C. A solution of sodium nitrite (1.26 g,18.3 mmol) in H₂O (10 ml) was transferred to a dropping funnel and addeddropwise to the reaction vessel over 2 h. After stirring for 2 h at 0°C., stannous chloride (8.3 g, 36.9 mmol; dissolved in 10 ml conc. HCl)was added dropwise over 2 h. The reaction mixture was then allowed towarm to room temperature and stirred overnight. The reaction mixture wasthen filtered and the filtrate discarded. The isolated solid was thentransferred to a round-bottomed flask and treated with acetic acid (15ml), potassium acetate (3 g) and 3-methyl-2-butanone (3 ml). Afterheating the vessel at 140° C. for 4 h, the reaction mixture wasconcentrated in vacuo and the resultant gum purified by RP-HPLC(Phenomenex Synergi; 10u hydro-RP 80, 250×21.20 mm; MeCN:H₂O; 0-100%MeCN 30 min; 10 ml/min, RT=14 min) to isolate the desired product (550mg; 2 mmol, 22%). MS (MALDI-TOF) MH⁺273.

16.23-(5-Carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

To a solution of 7-chloro-2,3,3-trimethyl-3H-indole-5-sulfonic acid (50mg; 0.18 mmol) in acetic acid/pyridine/acetic anhydride (4.5:4.5:1; 10ml) was added(2E)-3-(5-carboxypentyl)-7-chloro-3-methyl-1-pentyl-2-[(2E,4E)-4-(phenylimino)but-2-enylidene]indoline-5-sulfonate(110 mg; 0.18 mmol). The reaction mixture was heated at 60° C. for 4 hthen concentrated in vacuo to yield the crude dye. The resultant gum waspurified by prep RP-HPLC (Phenomenex Synergi; 10 u hydro-RP 80,250×21.20 mm; MeCN:H₂O; 0-100% MeCN 30 min; 10 ml/min, R=16 min) toyield the desired product (10 mg; 0.01 mmol; 7%). MS (MALDI-TOF) MH⁺783

16.33-(5-Carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium,N-hydroxysuccinimidyl ester

To a stirred solution of6-[(2E)-2-[(2E,4E)-5-(7-chloro-3,3-dimethyl-5-sulfo-3H-indol-2-yl)penta-2,4-dienylidene]-3-methyl-5-sulfo-1-(4-sulfobutyl)-2,3-dihydro-1H-indol-3-yl]hexanoicacid (9 mg; 0.01 mmol) in DMF (3 ml) was added DIPEA (2 ml) followed byO-(N-succinimidyl-N,N,N′,N′-bis-tetramethylene)uroniumhexafluorophosphate (14 mg; 0.05 mmol). After 4 h, the reaction mixturewas concentrated in vacuo and the resultant gum purified by RP-HPLC(Phenomenex Synergi; 10u hydro-RP 80, 250×21.20 mm; MeCN:H₂O; 0-100%MeCN 30 min; 10 ml/min, RT=17 min) to isolate the product (6 mg; 0.007mmol; 53%). Observed pKa in aqueous phosphate buffers (viafluorescence): 6.2. MS (MALDI-TOF) M+Na⁺902

17. Synthesis of3-(5-carboxypentyl)-3-methyl-2-{(1E,3E,5E)-5-[3-methyl-5-sulfo-3-(4-sulfobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-sulfo-1-(4-sulfobutyl)-3H-indolium

17.1 5-Methyl-6-oxoheptane-1-sulfonic acid

Ethyl 2-methylacetoacetate (43.2 g) in N,N-dimethylformamide (25 ml) wasadded to a suspension of sodium hydride (12.0 g of 60% NaH in mineraloil) in N,N-dimethylformamide (100 ml), dropwise with ice-bath cooling.This mixture was allowed to warm to ambient temperature for 30 minsbefore re-cooling. 1,4-butanesultone (40.8 g) in N,N-dimethylformamide(25 ml) was then added dropwise. The final mixture was heated at 50° C.for 18 hrs, then quenched with 50 ml of water. The solvent wasevaporated under vacuum; the residue was partitioned between water anddiethyl ether. The aqueous layer was collected, washed with freshdiethyl ether and evaporated under vacuum; final drying was under highvacuum over phosphorus pentoxide. A yield of 103 g of5-(ethoxycarbonyl)-5-methyl-6-oxoheptane-1-sulfonic acid was obtained.

This intermediate was dissolved in concentrated hydrochloric acid (200ml) and reacted at 90° C. for 3 hrs, then the solvent was evaporatedunder vacuum. The residue was purified by flash chromatography (silica.Dichloromethane→ethanol). Fractions containing the product were pooledand evaporated under vacuum to give the title compound, 49.6 g. ¹H-nmr(D₂O) δ1.05 (3H, d), 1.3-1.8 (6H, m), 2.20 (3H, s), 2.65 (1H, m), and2.90 (2H, m)

17.2 2,3-Dimethyl-3-(4-sulfobutyl)-3H-indole-5-sulfonic acid

4-Hydrazinobenzenesulfonic acid (1.88 g), 5-methyl-6-oxoheptanesulfonicacid (2.5 g) and acetic acid (50 ml) were mixed and heated under refluxfor 6 hrs. The solvent was evaporated under vacuum, then the residue wastriturated with 2-propanol to yield the crude product as a yellow solid.This was purified by HPLC as required (RPC₁₈. Water+0.1% TFA). ¹H-nmr(D₂O) δ0.8-1.0 (2H, m), 1.55-1.65 (5H,=3H, s+2H, m), 2.16 (1H, ddd),2.29 (1H, ddd), 2.75 (2H, m), 2.81 (partially d-exchanged methylsinglet), 7.71 (1H, d), 7.94 (1H, d) and 8.01 (1H, d). UV/Vis(Water+0.1% TFA): 269, 229 nm. MS (LCMS): MH⁺362. Acc. Mass: Found,362.0729. MH⁺=C₁₄H₂₀NO₆S₂ requires 362.0732 (−0.8 ppm).

17.33-(5-Carboxypentyl)-3-methyl-2-{(1E,3E,5E)-5-[3-methyl-5-sulfo-3-(4-sulfobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-sulfo-1-(4-sulfobutyl)-3H-indolium

4-{2-[(1E,3E)-4-Anilinobuta-1,3-dienyl]-3-(5-carboxypentyl)-3-methyl-5-sulfo-3H-indolium-1-yl}butane-1-sulfonate(made as in Example 14.2, 50 mg) and2,3-dimethyl-3-(4-sulfobutyl)-3H-indole-5-sulfonic acid (50 mg) weremixed in pyridine (2.25 ml), acetic acid (2.25 ml) and acetic anhydride(0.50 ml) and stirred at ambient temperature under nitrogen for 18 hrs,then for 2 hrs at 60° C. The resulting green-blue solution wasevaporated under vacuum. The residue was purified by HPLC (RPC₁₈.Water/MeCN/TFA gradient). Fractions containing the principal dye peakwere collected, pooled and evaporated under vacuum to give the titledye, 22 mg. UV/Vis (Water+0.1% TFA): 651 nm. MS (MALDI-TOF): M+872.

18. Synthesis of6-[9-(5-carboxypentyl)-5,7-dimethyl-5,11-disulfo-1,2,9,14,15,16,15a,16a,2a-nonahydroindolo-[2″,1″-1′,2′]isoquinolino[7′,6′-4,3]pyridino[1,2-a]indolin-7-yl/hexanoicacid (rigid Cy3)

To a stirred solution of6-(2,3-dimethyl-5-sulfo-3-hydroindol-3-yl)hexanoic acid (150 mg, 0.45mmol) in ethanol (20 ml) at ambient temperature was added hydrobromicacid (3 ml, 40% aqueous solution). After 1 hr the reaction solvent wasremoved in vacuo. The hydrobromide salt was redissolved in acetonitrile(20 ml) and acetic acid (200 ml) and acrolein diethyl acetal (10 g, 75mmol) was added. The reaction mixture was heated to 70° C. for 20minutes. The solution was cooled and the solvent removed in vacuo. Theproduct was rapidly purified on reverse phase C18 column using 1:1water/acetonitrile (containing 0.1% TFA) as solvent. All fractions weremonitored by RP C18 TLC. Fractions containing product were pooled.Evaporation of the solvent gave a sticky mass (120 mg, 36%). It wasimmediately used for the next reaction.

To a stirred solution of6-[1-(3,3-diethoxypropyl)-2,3-dimethyl-5-sulfo-3-hydroindole-3yl]hexanoic acid (100 mg, 0.21 mmol) in pyridine (5 ml) at 120° C. wasadded dropwise, triethyl orthoformate (100 mg, 67 mmol) over 30 minutes.After 2 hrs the reaction mixture was cooled. The product was purified byreversed phase C18 column using water-acetonitrile mixture (containing0.1% TFA) as solvent. The product was obtained as a pink solid (45 mg,40%); λmax: 560 nm water, λem 570 nm, φ0.09

To a stirred solution of1,1-di-(3,3-diethoxypropyl)-3-methyl-3′(6-carboxypentenyl)-indocarbocyanine(40 mg, 0.04 mmol) in ice water was added 50% aqueous sulphuric acid (2ml). The reaction mixture was heated at 40° C. for 30 minutes. Themixture was cooled and neutralized with triethylamine. Solvent wasremoved under vacuum on a flash evaporator was obtained as red solid.λmax 565 nm, λem 584 nm, φ0.8.

19. Synthesis of6,7,9,10-tetrahydro-2,14-disulphonato-16,16,18-trimethyl-7aH,8aH-bisindolinium[3,2-a,3′2′-a]pyrano[3,2-c;5,6-c′]dipyridin-5-ium-18-hexanoicacid

19.11-(3,3-Diethoxypropyl)-3-(6-ethoxy-6-oxohexyl)-2,3-dimethyl-3H-indolium-5-sulfonate

6-(2,3-Dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid was synthesised asdescribed in Example 5. To a stirred solution of6-(1-ethyl-2,3-dimethyl-5-sulfo-3H-indol-3-yl)hexanoic acid (1.8 g, 5.3mmol) in ethanol (200 ml) at ambient temperature was added hydrobromicacid (10 ml 48% aqueous solution). After 1 Hr the reaction solvent wasremoved in vacuo. The hydrobromide salt was re-dissolved in acetonitrile(150 ml) and acetic acid (1.54 ml) and acrolein diethyl acetal (6.6 g,51 mmol). The reaction mixture was heated to 70° C. for 30 minutes. Thesolution was cooled and the solvent removed in vacuum. The product wasrapidly purified by preparative HPLC on reverse phase C18 column usinggradient elution of water containing 10% acetonitrile to acetonitrile(containing 0.1% TFA) as solvent over 30 minutes. All fractions weremonitored by MALDI-TOF mass spectrometry (M/Z=498). Fractions containingproduct mass were pooled. Evaporation of the solvent gave a sticky mass(162 mg 11%). It was immediately used for the next reaction.

19.2 1-(3,3-Diethoxypropyl)-2,3,3-trimethyl-3H-indolium-5-sulphonate

Potassium 2,3,3-trimethyl-3H-indole-5-sulfonate was synthesisedfollowing the procedure described in Mujumdar, R, B Bioconjugate Chem.,(1993), 4(2), 105-111. To a stirred solution of potassium2,3,3-trimethyl-3H-indole-5-sulfonate (5 g, 18 mmol) in ethanol (250 ml)at ambient temperature was added hydrobromic acid (50 ml 48% aqueoussolution). After 1 Hr the reaction solvent was removed in vacuo. Thehydrobromide salt was re-dissolved in acetonitrile (200 ml) and aceticacid (5 ml) and acrolein diethyl acetal (42.25 g, 325 mmol). Thereaction mixture was heated to 70° C. for 60 minutes. The solution wascooled and the solvent removed in vacuum. The product was rapidlypurified by preparative HPLC on reverse phase C18 column using gradientelution of water containing 10% acetonitrile to acetonitrile over 60minutes (containing 0.1% TFA) as solvent. All fractions were monitoredby MALDI-ToF mass spectrometry (M/Z 369). Fractions containing productmass were pooled. Evaporation of the solvent gave a sticky mass (1.8 g36%). It was immediately used for the next reaction.

19.31-(3,3-diethoxypropyl)-2-{(1E,3E)-3-[1-(3,3diethoxypropyl)-3,3-dimethyl-5-sulfonato-1,3-dihydro-2H-indol-2-ylidene]prop-1-enyl}-3-(6-ethoxy-6-oxohexyl)-3-methyl-3H-indolium-5-sulfonate

To 120 mg (0.325 mmol) of1-(3,3-diethoxypropyl)-3-(6-ethoxy-6-oxohexyl)-2,3-dimethyl-3H-indolium-5-sulponatewas added pyridine (5 ml) to dissolve. To 162 mg (0.325 mmol)1-(3,3-diethoxypropyl)-2,3,3-trimethyl-3H-indolium-5-sulphonate wasadded pyridine (5 ml) to dissolve. The contents of the above flasks werecombined, stirred and triethylorthoformate (385 mg, 2.6 mmol) added. Thereaction mixture was heated to 120° C. for 5 Hr. The solution was cooledand the solvent removed in vacuum. The product was purified bypreparative HPLC on reverse phase C18 column using gradient elution ofwater to acetonitrile over 90 minutes (containing 0.1% TFA) as solvent.All fractions were monitored by MALDI-TOF mass spectrometry (M/Z=1006).Fractions containing product mass were pooled. Evaporation of thesolvent gave a pink solid (78 mg 13%). It was immediately used for thenext reaction.

19.4 6,7,9,10-tetrahydro-2,14-disulphonato-16,16,18-trimethyl-7aH,8aH-bisindolinium[3,2-a,3′2′-a]pyrano[3,2-c;5,6-c′]dipyridin-5-ium-18-hexanoicacid

78 mg (8.88×10⁻⁵ mol) of 1-(3,3-diethoxypropyl)-2-{(1E,3E)-3-[1-(3,3-diethoxypropyl)-3,3-dimethyl-5-sulfonato-1,3-dihydro-2H-indol-2-ylidene]prop-1-enyl}-3-(6-ethoxy-6-oxohexyl)-3-methyl-3H-indolium-5-sulfonatewas dissolved in sulphuric acid (2 ml 48% aqueous solution) and stirredat ambient temperature for 4 hours. The solvent was removed undervacuum. The product was purified by preparative HPLC on reverse phaseC18 column using gradient elution over 90 minutes of water toacetonitrile (containing 0.1% TFA) as solvent. All fractions weremonitored by MALDI-TOF mass spectrometry. Fractions containing theproduct mass were pooled. Evaporation of the solvent gave a pink solid(27 mg 35%).

20. General Protein Labeling Procedure

The following protein labeling procedure was followed to label sheep IgGwith NHS ester of Cy3.10, Cy3.24, NSCy3, Cy7.18 and NSCy7. Stocksolutions of the succinimidyl active esters were made in dry DMF(0.3-1.0 mg active ester/100 μL) and are stable for days when stored at4° C. The active esters are also stable in distilled water for severalhours provided the pH of the solution is not basic. Aqueous solutions ofthe dyes can be used for labeling antibodies if the use of DMF is notsuitable for certain antibodies. The concentration of cyaninefluorophore in the stock solution was determined by measuring theabsorbance of an aliquot of the appropriately diluted stock solution inphosphate-buffered saline (PBS) and using the extinction coefficient ofthe dye. The stock solution concentration of cyanine fluorophore in theactive ester form was then determined by reverse-phase HPLC (typically50-95% but sometimes as low as 35%). The antibody labeling was carriedout in 0.1M carbonate-bicarbonate buffer (pH 9.4) for 15 minutes at roomtemperature. The sheep IgG (1 mg, 6.45 mM) was dissolved in 0.25-1 mLbuffer solution and the desired amount of dye (e.g., 20 μL of stockcontaining 0.35 mg active ester/100 μL DMF) was added during vigorousvortex mixing. Unconjugated dye was separated from the labeled proteinby gel permeation chromatography (0.7×20 cm column of Sephadex G-50)using pH 7 buffer solution as eluent.

21. Determination of Dye-to-Antibody Ratio

A simple method for estimating dye/protein (d/p) ratios involves directmeasurement of the protein absorbance at 280 nm and dye absorbance atthe absorption maximum. Specifically, the dye/protein ratio iscalculated using the equation below with measured values of theabsorbance of the labeled dye (Cy3 at 550 nm or Cy7 at 750 nm) and theabsorbance of protein at 280 nm. The extinction coefficients of Cy3 andCy7 are approximately 150,000 and 250,000 respectively. The extinctioncoefficient of the IgG antibody at 280 nm was taken to be 170,000L/mol-cm. The factor “X” in the denominator accounts for dye absorptionat 280 nm which is 0.05 (for both Cy3) and 0.08 (for Cy7) of theabsorption of the dye at its maximum absorption (A_(dye)).

$\frac{D}{P} = \frac{A_{dye}*E_{prot}}{\left( {A_{280} - {0.05A_{dye}}} \right)*E_{dye}}$

A more accurate method is needed when the labeling reagent showssignificant spectral changes when bound to the antibody molecule. Forexample, this approach is needed when both dimers and monomers of dye,which have different absorption peaks and different extinctioncoefficients, are present on the protein at higher d/p ratios. In thiscase, the labeled protein is dissolved in formamide for absorptionspectroscopy and the extinction coefficients of the dye determinedindependently for the calculation

22. Measurement of pKa Values of pH-Sensitive Cyanine Dyes

The general method of pKa determination was performed as follows.Purified dye was dissolved in water to give a bulk stock solution (ifnecessary, a limited amount of acetonitrile was added to ensuresolubility). By experiment, the volume of this stock solution that wasrequired to be added to 10.0 ml of water+0.1% v/v trifluoroacetic acid,in order to give an absorbance of 0.5±0.02 at the dye peak wavelength,was determined. This volume of bulk stock solution was then added to10.0 ml of water, to be used as the working stock solution.

Aqueous phosphate buffers were prepared covering the region of pH 4-9{see “Data for Biochemical Research”, p. 432, 3^(rd) edition, R. M. CDawson, D. C. Elliott, W. H. Elliott & K. M. Jones, 1987 OxfordUniversity Press. Buffers outside the listed range were made by addingin orthophosphoric acid or sodium hydroxide}. Plastic fluorescencecuvettes were then charged with 3.5 ml of each buffer. A fixed volume ofdye working stock solution (in the range 50-250 μl) was added to acuvette of buffer, the solution mixed and the fluorescence signalmeasured immediately {Perkin Elmer LS55 fluorimeter, excitation 640 nm.Emission spectrum was scanned and fluorescence intensity value at 680 nmrecorded}. This was repeated for all cuvettes. The graph of fluorescenceintensity versus pH was plotted using PRISM, the data fitted to asigmoidal dose-response curve and the pKa value extracted as thecalculated IC50 value from the fitting.

Table 1 lists the pKa values of the carboxy dyes prepared in the abovefour examples, along with a selection of non-functional dyes (dyes 5-9)that were prepared using the same methodology. These extra examples helpto explain the effect of substitution on the observed pKa value of thedye chromophore, and show that this figure can be tuned to any valueacross the physiological pH range.

TABLE 1 No Name Structure pKa 1 2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

7.0 2 3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

6.05 3 2-{(1E,3E,5E)-5-[-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium

7.44 4 3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

6.2 5 2-[(1E,3E,5E)-5-(3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H- indolium

7.0 6 2-[(1E,3E,5E)-5-(3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3- dienyl]-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium

7.0 7 2-[(1E,3E,5E)-5-(5-chloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3,3-dimethyl-5-sulfo-1-(4- sulfobutyl)-3H-indolium

6.65 8 2-[(1E,3E,5E)-5-(5-cyano-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3,3-dimethyl-5-sulfo-1-(4- sulfobutyl)-3H-indolium

6.65 9 5-chloro-2-[(1E,3E,5E)-5-(3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2- ylidene)penta-1,3-dienyl]-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium

7.36

Comparison of dyes 5 and 6 show that substitution of H for sulfonate, inthe position para- to the unquaternized nitrogen, has no measureableeffect on dye pKa. Furthermore, dye 1 shows that addition of thefunctional arm onto dye 6 has no measurable effect on dye pKa.

Comparison of the above dye set with dyes 7,4 and 2 shows the effect ofincorporating an electron-withdrawing group, such as Cl, onto theunquaternized indolenine unit. Substitution of Cl para- to theunquaternized nitrogen lowers the dye pKa by 0.3-0.4 units (dye 1→dye7). Substitution of Cl ortho- to the unquaternized nitrogen lowers thedye pKa by ˜0.8 units (dye 1→dye 4). Incorporating both substitutionsgives an additive effect, lowering the pKa by ˜1.0 unit (dye 1→dye 2).Dye 8 shows that another electron-withdrawing group, cyano, has asimilar effect to chloro. Fluoro and trifluoromethyl act similarly.

Comparison of dyes 9 and 3 with dyes 6, 7 and 1 shows the effect ofincorporating an electron-withdrawing group, such as Cl, onto thequaternized indolenine unit. Substitution of Cl para- to the quaternizednitrogen raises the dye pKa by 0.3-0.4 units. Hence the pKa of thesepH-sensitive dyes can be adjusted from that of the base structures, atpKa=7.0, in either direction by the considered placement ofelectron-withdrawing groups such as chloro (fluoro, cyano,trifluoromethyl).

The contents of references cited herein are incorporated herein byreference in their entirety.

1. A compound of the following general formula (XIII)

wherein R_(a), R_(c), R_(d) and R_(f) are independently selected fromhydrogen, halogen and —SO₃ ⁻; R_(b) is selected from V or L-V, where Lis a bond or C₁₋₂₂ straight or branched alkyl, optionally containing 0,1 or 2 unsaturations or unsaturated pendent or interchain groupsselected from alkenyl, alkynyl and aryl groups; and V is selected fromhydrogen, —SO₃ ⁻, —COOH and a reactive group; R_(e) is hydrogen; T is

wherein each L and V are independently as defined above; Y is selectedfrom the group consisting of O, S, —CH═CH—, >C(CH₃)₂, and

wherein each L and V are independently as defined above; Z_(a) and Z_(b)are, independently, fused

n is an integer from 1-4; and p, u, v and r are independently an integerfrom 0-4, wherein at least one group -L-V in groups T and/or Y is asubstituted alkyl group.
 2. A compound of the following general formula(XIII)

wherein R_(a), R_(c), R_(d) and R_(f) are independently selected fromhydrogen, halogen and —SO₃ ⁻; R_(b) is selected from V or L-V, where Lis a bond or C₁₋₂₂ straight or branched alkyl, optionally containing 0,1 or 2 unsaturations or unsaturated pendent or interchain groupsselected from alkenyl, alkynyl and aryl groups; and V is selected fromhydrogen, —SO₃ ⁻, —COOH and a reactive group; R_(e) is hydrogen; T is

wherein each L and V are independently as defined above; Y is selectedfrom the group consisting of O, S, —CH═CH, <C(CH₃)₂, and

wherein each L and V are independently as defined above; Z_(a) and Z_(b)are, independently, fused

n is an integer from 1-4; and p, u, v and r are independently an integerfrom 0-4, wherein said at least one group -L-V in groups T and/or Y isselected from a carboxyalkyl group, a sulfoalkyl group and a reactivegroup.
 3. A compound of claim 1 or claim 2 wherein said reactive groupis selected from:

where n is an integer of 1-10, and Q and W are leaving groups.
 4. Amethod for detecting acidic or basic conditions comprising contacting acompound according to claim 1 or claim 2 with a composition suspected ofbeing acidic or basic and detecting the fluorescence of said compound asan indicator of said acidic or basic conditions.
 5. The method accordingto claim 4 wherein said composition comprises an intracellularenvironment.
 6. A compound selected from the group consisting of: i)2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-3,3-dimethyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium;ii)3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(5,7-dichloro-3,3-dimethyl-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H-indolium;iii)2-{(1E,3E,5E)-5-[3-(5-carboxypentyl)-3-methyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-chloro-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium;iv) 3-(5-carboxypentyl)-2-[(1E,3E,5E)-5-(7-chloro-3,3-dimethyl-5-sulfo-1,3-dihydro-2H-indol-2-ylidene)penta-1,3-dienyl]-3-methyl-5-sulfo-1-(4-sulfobutyl)-3H -indolium; and v)3-(5-carboxypentyl)-3-methyl-2-{(1E,3E,5E)-5-[3-methyl-5-sulfo-3-(4-sulfobutyl)-1,3-dihydro-2H-indol-2-ylidene]penta-1,3-dienyl}-5-sulfo-1-(4-sulfobutyl)-3H-indolium.
 7. A method for labelling and detecting a component of anaqueous liquid comprising: a) adding to said liquid containing saidcomponent a compound of claim 1 or claim 2 which compound is reactivewith said component; b) reacting said compound with said component sothat said compound becomes bound to and thereby labels said component;and c) detecting said labeled component by an optical method.
 8. Themethod of claim 7 wherein said component is selected from any one of anantibody, protein, peptide, enzyme substrate, hormone, lymphokine,metabolite, receptor, antigen, hapten, lectin, avidin, streptavidin,toxin, carbohydrate, oligosaccharide, polysaccharide, nucleic acid,derivatized deoxy nucleic acid, DNA fragment, RNA fragment, derivatizedDNA fragment, derivatized RNA fragment, nucleoside, nucleotide, naturaldrug, synthetic drug, virus particle, bacterial particle, viruscomponent, yeast component, blood cell, blood cell component, plasmacomponent, serum component, biological cell, noncellular bloodcomponent, bacteria, bacterial component, natural or synthetic lipidvesicle, poison, environmental pollutant, polymer, polymer particle,glass particle, glass surface, plastic particle, plastic surface,polymer membrane, conductor or semiconductor.
 9. A compound of claim 3wherein Q and W are independently selected from the group consisting ofl, Br and Cl.